In general terms, an oil well pumping system begins with an above-ground pumping unit, which creates the up and down pumping action that moves the oil (or other substance being pumped) out of the ground and into a flow line, from which the oil is taken to a storage tank or other such structure.
Below ground, a shaft is lined with piping know as “tubing.” A sucker rod, which is ultimately, indirectly coupled at its north end to the pumping unit is inserted into the tubing. The sucker rod is coupled at its south end indirectly to the oil pump itself, which is also located within the tubing, which is sealed at its base to the tubing. The sucker rod couples to the oil pump at a coupling known as a 3-wing cage.
Beginning at the south end, oil pumps generally include a standing valve, which has a ball therein, the purpose of which is to regulate the passage of oil (or other substance being pumped) from downhole into the pump, allowing the pumped matter to be moved northward out of the system and into the flow line, while preventing the pumped matter from dropping back southward into the hole. Oil is permitted to pass through the standing valve and into the pump by the movement of the ball off of its seat, and oil is prevented from dropping back into the hole by the seating of the ball.
North of the standing valve, coupled to the sucker rod, is a traveling valve. The purpose of the conventional traveling valve is to regulate the passage of oil from within the pump northward in the direction of the flow line, while preventing the pumped oil from slipping back down in the direction of the standing valve and hole.
In use, oil is pumped from a hole through a series of “downstrokes” and “upstrokes” of the oil pump, wherein these motions are imparted by the above-ground pumping unit. During the upstroke, formation pressure causes the ball in the standing valve to move upward, allowing the oil to pass through the standing valve and into the barrel of the oil pump. This oil will be held in place between the standing valve and the traveling valve. In the conventional traveling valve, the ball is located in the seated position. It is held there by the pressure from the oil that has been previously pumped. The oil located above the traveling valve is moved northward in the direction of the 3-wing cage at the end of the oil pump.
During the downstroke, the ball in the conventional traveling valve unseats, permitting the oil that has passed through the standing valve to pass therethrough. Also during the downstroke, the ball in the standing valve seats, preventing the pumped oil from slipping back down into the hole.
The process repeats itself again and again, with oil essentially being moved in stages from the hole, to above the standing valve and in the oil pump, to above the travelling valve and out of the oil pump. As the oil pump fills, the oil passes through the 3-wing cage and into the tubing. As the tubing is filled, the oil passes into the flow line, from which the oil is taken to a storage tank or other such structure.
There are a number of problems that are regularly encountered during oil pumping operations. Oil that is pumped from the ground is generally impure, and includes water, gas, and impurities such as sand. During pump operations, the presence of gas in the oil can create a condition that is sometimes referred to as “gas lock.” Gas lock occurs when a quantity of gas becomes trapped between the traveling valve and standing valve balls. In this situation, hydrostatic pressure from above the traveling valve ball holds it in a seated position, while the pressure from the trapped gas will hold the standing valve ball in a seated position. With the balls unable to unseat, pumping comes to a halt.
The typical response to a gas lock is to remove the oil pump and release the trapped gas. This can be time-consuming and, of course, interrupts pumping operations.
Another problem is related to the ball and seat for the ball within the traveling valve. During pumping operations, the ball is continuously being lifted off the seat, rotating, and re-seating. However, because the traveling valve ball is not coupled to the seat, it does not always perfectly center when seating. This can result in some leakage in the traveling valve and thus pumping inefficiency. Moreover, improper seating can cause damage to both the ball and the seat, which are the shortest wear items in the oil pump. When these are sufficiently worn, pumping operations must be interrupted and the entire oil pump removed for their replacement. Relatedly, while the seat can be inverted to extend its life, the constant rotation of the ball results in substantially even wear over the entire surface of the ball, making inversion to extend ball life impossible.
Still another problem is related to the impurities commonly found in the oil, such as sand. Sand can become trapped between the side of the traveling valve and the interior wall of the oil pump. When it becomes trapped in this manner, the constant up and down motion of the traveling valve can lead to scoring of the traveling valve, ultimately reducing its effectiveness and sometimes requiring its replacement. Sand can also get between the ball and seat, preventing proper seating, possibly leading to damage and inefficiency.
Yet another problem is encountered during deviated or non-vertical pumping operations. It is often necessary to conduct pumping operations in an angled or even horizontal direction, where for one reason or another, e.g., where a building is located directly over the hole, it is impossible to access the hole from directly above. In these instances, a well is sunk vertically at a distance from the site, and the well (including the oil pump) is then extended at an angle or perhaps even horizontally to the hole. Where the oil pump is operating in a non-vertical orientation, the traveling valve ball will be pulled by gravitational forces toward the side of the traveling valve, preventing it from fully seating, potentially causing damage and inefficiency.
The pumping of heavy crude also presents problems. The viscosity of this fluid can prevent the traveling valve ball from seating as quickly as it should for optimal performance. This reduces pumping efficiency.
A solution to the above-mentioned problems was disclosed in U.S. Pat. No. 6,481,987, which was issued to the inventor herein on Nov. 19, 2002. However, when using the traveling valve disclosed in U.S. Pat. No. 6,481,987, oil that is present within the mini drag plunger at the completion of a downstroke may be left behind in the pump barrel during the occurrence of the next upstroke. The amount of oil that is left behind in the pump barrel is the same amount of new oil, therefore, that cannot be drawn into the pump barrel through the standing valve during the next upstroke. Cumulatively, this may lead to a large amount of oil that is not being produced from the pump barrel during each downstroke/upstroke pump cycle. For example, at a rate of 10 strokes per minute, in one month, the amount of oil left behind in the pump barrel could amount to over 200 barrels of fluid not being pumped.
The present invention addresses these problems encountered in the prior art pumping systems by eliminating gas lock, minimizing pump damage caused by solids in the fluid, and recovering fluid slippage as well as other related advantages.